Engineering Manual

REFRIGERANT PIPING DESIGN
Refrigerant Charge
LG Multi F and Multi F MAX outdoor units ship from the factory with a charge of
R410A refrigerant. A trim charge may need to be added to take into account
additional piping length.
To determine the additional refrigerant that is needed, apply the formulas below,
and record the results. If the total additional refrigerant charge value is a negative
number, then an additional trim charge does not need to be added to the system.
Additional charge (lbs.) = (Installed Length of Branch [A] – Chargeless Pipe Length [L]) x a
+ (Installed Length of Branch [B] – Chargeless Pipe Length [L]) x a
+ (Installed Length of Branch [C] – Chargeless Pipe Length [L]) x a
+ (Installed Length of Branch [D] – Chargeless Pipe Length [L]) x a
- CF (Correction Factor) x 5.29
Outdoor Unit Model
Min. to Max. Piping Length
for One Branch (ft.)
Max. Total System Piping
Length (ft.)
Chargeless Pipe Length
per Branch (L) (ft.)
Additional Charge Needed
(a) (oz./ft.)
LMU18CHV 10 to 82 164 24.6 0.22
LMU24CHV 10 to 82 246.1 24.6 0.22
LMU36CHV 10 to 82 246.1 24.6 0.22
Outdoor Unit
Factory Charge
lbs. of R410A
LMU18CHV 3.96
LMU24CHV 3.96
LMU36CHV 6.18
LMU540HV 9.7
Table 111:Outdoor Unit Factory Charge.
Multi F Systems
• Number of installed length of branches depends on the specifications of the outdoor unit model.
• CF = Maximum number of connectable indoor units – Total number of connected indoor units.
Table 112:Multi F Outdoor Unit Piping Specications.
Figure 262:Multi F Additional Refrigerant Charge Example.
Each branch pipe
A = 82 ft.
B = 16 ft.
C = 49 ft.
Additional Charge
A
B
C
9,000
9,000
9,000
Example: LMU36CHV
= (82 - 24.6) x 0.22
+ (16 - 24.6) x 0.22
+ (49 - 24.6) x 0.22
- (4 - 3) x 5.29
= 10.82 oz.
Due to our policy of continuous product innovation, some specications may change without notication.
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196 | DESIGN & PRACTICES
Multi F and Multi F MAX Indoor Unit Engineering Manual
MULTI
F
MAX
MULTI
F